SummaryMaintaining potassium (K + ) nutrition and a robust guard cell K + inward channel activity is considered critical for plants' adaptation to fluctuating and challenging growth environment. ABA induces stomatal closure through hydrogen peroxide and nitric oxide (NO) along with subsequent ion channel-mediated loss of K + and anions. However, the interactions of NO synthesis and signalling with K + nutrition and guard cell K + channel activities have not been fully explored in Arabidopsis. Physiological and molecular techniques were employed to dissect the interaction of nitrogen and potassium nutrition in regulating stomatal opening, CO 2 assimilation and ion channel activity. These data, gene expression and ABA signalling transduction were compared in wildtype Columbia-0 (Col-0) and the nitrate reductase mutant nia1nia2.Growth and K + nutrition were impaired along with stomatal behaviour, membrane transport, and expression of genes associated with ABA signalling in the nia1nia2 mutant. ABA-inhibited K + in current and ABA-enhanced slow anion current were absent in nia1nia2. Exogenous NO restored regulation of these channels for complete stomatal closure in nia1nia2.While NO is an important signalling component in ABA-induced stomatal closure in Arabidopsis, our findings demonstrate a more complex interaction associating potassium nutrition and nitrogen metabolism in the nia1nia2 mutant that affects stomatal function.

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Soil salinity is an environmental and agricultural problem in many parts of the world. One of the keys to breeding barley for adaptation to salinity lies in a better understanding of the genetic control of stomatal regulation. We have employed a range of physiological (stomata assay, gas exchange, phylogenetic analysis, QTL analysis), and molecular techniques (RT-PCR and qPCR) to investigate stomatal behavior and genotypic variation in barley cultivars and a genetic population in four experimental trials. A set of relatively efficient and reliable methods were developed for the characterization of stomatal behavior of a large number of varieties and genetic lines. Furthermore, we found a large genetic variation of gas exchange and stomatal traits in barley in response to salinity stress. Salt-tolerant cultivar CM72 showed significantly larger stomatal aperture under 200 mM NaCl treatment than that of salt-sensitive cultivar Gairdner. Stomatal traits such as aperture width/length were found to significantly correlate with grain yield under salt treatment. Phenotypic characterization and QTL analysis of a segregating double haploid population of the CM72/Gairdner resulted in the identification of significant stomatal traits-related QTLs for salt tolerance. Moreover, expression analysis of the slow anion channel genes HvSLAH1 and HvSLAC1 demonstrated that their up-regulation is linked to higher barley grain yield in the field.

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BackgroundStomata regulate photosynthesis and transpiration, and these processes are critical for plant responses to abiotic stresses such as salinity. A barley double haploid population with 108 lines derived from a cross between CM72 (salt-tolerant) and Gairdner (salt-sensitive) was used to detect quantitative trait loci (QTLs) associated with stomatal and photosynthetic traits related to salinity tolerance.ResultsA total of 11 significant QTLs (LOD > 3.0) and 11 tentative QTLs (2.5 < LOD < 3.0) were identified. These QTLs are distributed on all the seven chromosomes, except 5H and explain 9.5–17.3% of the phenotypic variation. QTLs for biomass, intercellular CO2 concentration, transpiration rate and stomatal conductance under control conditions co-localised together. A QTL for biomass also co-located with one for transpiration rate under salinity stress. A linkage was found between stomatal pore area and gas exchange. A QTL for salinity tolerance also co-localised with QTLs for grain yield and biomass on chromosome 3H. Based on the draft barley genome, the candidate genes for salinity tolerance at this locus are proposed.ConclusionsThe lack of major QTLs for gas exchange and stomatal traits under control and saline conditions indicates a complex relationship between salinity and leaf gas exchange due to the fact that these complex quantitative traits are under the control of multiple genes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3380-0) contains supplementary material, which is available to authorized users.